1. Field of the Invention
The present invention relates to a package structure and a packaging method of a micro-electromechanical (MEMS) microphone.
2. Description of Related Art
Under the influence of the popular global communication, it is common that one person may have one or more mobile phones or everyone has a mobile phone. Even students carry mobile phones to school for communicating with parents, and thus the mobile phone consumer age is significantly lowered to below 10-year old.
Further, the Topology Research Institute points out in the September 2005 research report that the global shipment quantity of the mobile phones in 2005 was about 760 million, and the number of mobile phone users may reach up to 1.685 billion. The Topology also predicts that the global mobile phone users may be up to 2.236 billion. Therefore, the market scale of mobile phone application cannot be ignored.
Along with the increasing demands for video and audio functions, currently, in mobile phones worldwide, a new microphone, in addition to the microphone used for talking, is provided for the capturing video images, so as to provide convenience in service use. Therefore, the demand for the microphone grows increasingly.
The MEMS microphone has a thin thickness and small volume. Furthermore, the surface adhering process can be performed by solder reflow to effectively reduce the assembly cost. Therefore, in order to meet the requirements of the mobile phone with small volume and low cost, the MEMS microphone applied to gradually replace the original electric condenser microphone (ECM) on the market.
Moreover, the MEMS microphone has an innate advantage of low power consumption (160 μA) that is ⅓ of that of ECM. When applied in the mobile phones with limited power storage, this power saving advantage promotes the MEMS microphone to replace the ECM.
For other products equipped with microphone, the demands for the MEMS microphone tend to grow. For example, currently, the MEMS microphone is increasingly applied in electronic products such as portable walkman and digital camera for micro hard disks and flash memories. Therefore, in the future, it is possible for the MEMS microphone to have a considerable market in the electrical application fields.
For the current MEMS microphone, referring to FIG. 1, a sectional view of the current Knowles MEMS microphone module structure is shown.
A MEMS microphone chip 10 and a logic chip 20 are electrically coupled to a base plate 30. By using a conductive glue 32, a support ring 40 and a top plate 50 are successively stacked on the base plate 30, so as to constitute one acoustic wave cavity space V1 (referring to FIG. 2). The MEMS microphone chip 10 has an acoustic wave sensing portion 12, and the top plate 50 has an opening 52 for allowing the acoustic wave to enter or exit out of the acoustic wave cavity space V1 to be sensed by the acoustic wave sensing portion 12. In the acoustic wave cavity space V1, a liquid compound 34 is sealed on the logic chip 20 by using a dispensing process, so as to protect the logic chip 20 and the contacts to the base plate 30. The liquid compound 34 cannot be dispensed onto the MEMS microphone chip 10 since once being dispensed on the MEMS microphone chip 10, the liquid compound 34 may flow onto the acoustic wave sensing portion 12, further affecting the performance of the MEMS microphone module.
Referring to FIG. 3, a sectional view of the MEMS microphone module structure disclosed in the U.S. Pat. No. 6,781,231 B2 according to another conventional art is shown.
A conductive housing 120 having a sound-hole 144 in the middle thereof is adopted. The housing 120 can be integrated as a whole or a combination structure of constructed by stacking through two stages. The housing 120 is used to protect the MEMS microphone chip 110 and the logic element 112 therebeneath. The conductive housing 120 and all the elements under the conductive housing 120 are not filled with any material in between. That is, all the space under the conducting housing 120 can be used as the acoustic wave transmitting space (the volume V2 of acoustic wave cavity, referring to FIG. 4).
As far as the module assembly is concerned, the sealed bonding of the integrally fabricated conductive housing 120 and the substrate 114 therebeneath is achieved by using an adhesive and a solder for one monomer at a single time. The two-stage stacked conductive housings 125a, 125b are successively selected and placed one by one and bonded by two stages. Moreover, for the solder wire of electrical interconnection in the package, the monomer dispensing method is used to dispense the liquid epoxy resin individually in the area assembled with the solder wire, and then a heating hardening process is performed to cure the epoxy resin, so as to achieve the purpose of protecting the solder wire.
Similarly, based on the above reasons, the dispensing protection cannot be used for the MEMS microphone chip.
Also, in the current technique, the MEMS microphone chip is disposed in the acoustic wave cavity space, and is not protected by the molding compound, thus resulting in the following disadvantages.
(1) If the MEMS microphone module falls onto the ground (for example the mobile phone drops onto the ground), because the solder wire contacts of the MEMS microphone chip is not protected by the molding compound and may get damaged, and the reliability of the microphone is adversely affected.
(2) The external damp easily enters from the opening (sound-hole), and affects contacts to the substrate, so that the reliability of the module is reduced.